1. Technical Field
The present invention relates to a thin film transistor substrate, and more particularly, to a thin film transistor substrate capable of preventing flicker and improving reflectance, a liquid crystal display panel including the same, and a method of manufacturing the liquid crystal display panel.
2. Discussion of the Related Art
A liquid crystal display (LCD) device displays an image by using electrical and optical properties of liquid crystals. The LCD device includes an LCD panel for displaying an image through a pixel matrix, a driving circuit for driving the LCD panel, and a backlight unit for supplying light to the LCD panel. The LCD device is widely used ranging from small-sized display devices to large-sized display devices, such as mobile communication terminals, notebook computers, monitors and LCD TVs.
The LCD device may be classified according to a type of light source into a transmissive type using an internal light, a reflective type using an external light, and a transflective type using both the internal light and the external light. The transflective LCD device displays an image in a reflective mode if the external light is sufficient, and in a transmissive mode using a backlight unit if the external light is insufficient. Therefore, the transflective LCD device reduces power consumption and is not restricted to using external light.
The transflective LCD device has a structure in which a lower substrate 1 faces an upper substrate 11 with liquid crystal molecules 20 of an optically compensated bend (OCB) mode disposed therebetween, as illustrated in FIG. 1.
On the lower substrate 1, a reflective electrode 8 and a pixel electrode 10A of a first subpixel area face a pixel electrode 10B of a second subpixel with a gate line 4 disposed therebetween, the gate line being covered by an insulation layer 6.
A black matrix 2 separating the respective subpixel areas from each other, a color filter 16 formed in each subpixel area, an overcoat layer 14 having different thickness in a reflective area and a transmissive area, and a common electrode 12 forming a vertical electric field with respect to the pixel electrodes 10A and 10B and the reflective electrode 8, are formed on the upper substrate 11.
Due to an electric field formed between the common electrode 12 (or between the reflective electrode 8) and the gate line 4, an arrangement of the liquid crystal molecules 20 is changed, for example, inverted, at an edge of the reflective electrode 8 (or of the gate line 4). Since an arrangement of the liquid crystal molecules 20 at an edge of the reflective electrode 8 is different than in the other areas, light leakage occurs at the edge of the reflective electrode 8, resulting in flickering. Light leakage may be more severe in a line inversion scheme that supplies data voltages of different polarities to the adjacent pixel electrodes 10A and 10B with the gate line 4 disposed therebetween.
If the black matrix 2 is widened to partially overlap the first subpixel area so that an edge of the reflective electrode 8 can be blocked in order to prevent the light leakage, reflectance is lowered due to a decrease in an effective area of the reflective electrode 8.